Lubricating oil composition



Patented July 10,1945

"UNITED STATES PATENT osrics 2386.304 LUaarcA'rmG OIL COMPOSITION Anthony H. Gleason, Westfield, N. J., asslgnor to Standard Oil Development Company, a corporation of Delaware- 8 Claims.

This invention relates to mineral lubricating oil compositions of good viscosity characteristics. It relates'particularly to the blending of new type synthetic compounds in mineral lubricating oils as a means of preparing improved lubricatcording to this scale, the viscosity of an oil is determined accurately at two temperatures, namely, 100 F. and 210 F. in ,Saybolt Universal seconds, and comparison is made of the values at such temperatures with the viscosities of certain standard oils. If an oil has a low viscosity index,

' that is, the viscosity changes rapidly with temperature, indication is provided that the oil may be unsatisfactory as a lubricant, since at one temperature it may be so highly viscous as to present difliculty for engine starting, while at the temperature of engine operation, it may be so thin as to be wholly unsuited for lubricating the engine parts. Similarly, a low viscosity may indicate a relatively satisfactory lubricant at ordinary atmospheric temperature, but a wholly unsuitable lubricant at lower or higher temperatures due to excessive viscosity changes.

As regards viscosity characteristics in general, paraflin base oils are particularly advantageous. Asphaltic base oils, on the other hand, are considerably less satisfactory. Improvements in viscosity may be effected on both types of oil,'how- Refining oils to ever, by refining treatment. improve viscosity index is, however, beset with. many limitations, since intensive treatment causes chemical instability in the oil, especially as regards resistance to breakdown in a heated oxygen-containing atmosphere in the presence of metallic surfaces. Usually, it is generally considered more advantageous to refine oils to a limited extent, that is, to remove the more unstable and color-forming bodies and to' eflect further improvements by the addition of particularly eflective compounds. It is to this latter field that the present invention relates.

The addition of extraneous compounds to lubricating oils to improve their viscosity temperature relationship is a well-developed art. In the use and testing of the various blended composition's, it hasbeen clearly established that a compound, to be advantageous as an additive agent, must have certain properties. Such properties are that the compound must be satisfactorily soluble in the oil, that it be effective in relatively low concentrations, and that it be substantially stable under conditionsof usage to which the blended composition is subjected in service.

Polymeric compounds of simple hydrocarbons have been extensively investigated as a class as regards their suitability as lubricating oil addition agents. Two types of polymeric compounds are, however, to be recognized. When a'simple olefin or other bifunctional compound is polymerized, the polymer formed is usually of the nature of a purely additive product, that is, the molecular structure is theoretically considered asconsisting oflong chains or threads of recurringunits. Such a linear structure is in direct contrast to the molecular structure of a compound in which a three-dimensional molecular arrange- I ment is believed to exist.

Such difierences in molecular structure are believed to be the determining feature in the relative solubility and effectiveness as a viscosity improving agent of a polymer compound in min eral lubricating oils. The linear chain, twodimensional polymers are as a group, enerally highly viscous liquids and generally soluble in mineral lubricating oils, while the three-dimensional polymers are resinous materials and relatively insoluble in lubricating oils. The additive agent of this invention is a linear type polymeric compound sumciently satisfactorily soluble in lubricating oils as to be effective as a viscosity index improving agent. The polymeric compound of this invention is employed in a concentration between 0.5% and 5% by weight of the oil and preferably between 0.75% and 3.5% by weight of the oil.

Thus, it has been found that the copolymerization of a diolefin, such as 2,3-dime'thyl butadiene with a polyme'rizable unsaturated ester such as dodecyl methacrylate, in thepresence of a polymerizing agent, such as benzoyl peroxide, provides a product material which may be used advantageously as a viscosity index improving agent. The I-3-diolefins in generalare suitable for the preparation of this product material, but particularly suited are the lower aliphatic diolefins such as butadiene, isoprene and 2-3 dimethyl butadiene compounds having a conjugated structure of which theoleflnic groups are terminal.

A variety of unsaturated readily polymerizable esters may be employed. Suitable esters are those mainly cf the readily polymerizable acids provided the alcoholic portion possesses sufllcient chain length as to impart to the compound as a whole mineral oil solubility. Thus, the alcoholic portion is preferably of at least eight carbon atoms. Unsaturated alcohols are not generally employed since the presence of such groupings tends to increase the formation of cross-linkages between constituent polymer chains (three dimensional structure) with the resultant decrease in mineral oil solubility and viscosity index improvement. The acidic constituent of the unsaturated ester is usually acrylic acid or an asubstituted homolog. Cinnamic acid, fumaric acid, itaconic acid and methylene malonic acid may, however, also be advantageously employed.

The co-polymerization of the ester and diolefln may be effected in bulk by heating to between about 100 C. and 130 C. in the presence of a catalyst such as benzoyl peroxide or by employing the emulsion technique. Analyses of the products indicate that the mole ratio of diolefin to ester therein is usually about 5 to 3. Thus, a co-polymer of butadiene and octyl cinnamate was prepared by emulsifying 60 grams of butadiene and 35 grams of octyl cinnamate in 180 grams of a 2% solution of lauryl amine'hydrochloride containing one gram of potassium persulfate and 0.5 gram of lauryl mercaptan and heating the emulsion at 50-55 C. for about 36 hours. A coagulate was thus obtained which analyzed as indicating a copolymer of butadiene and octyl cinnamate.

The product was also soluble in mineral oil and.

effective as a V. I. improver.

As a particular illustration of the invention, equal parts of dodecyl methacrylate and 2,3-dimethyl butadiene were mixed and 1% of benzoyl peroxide was added. The mixture was heated at 105 C. for about two days. The product was a highly viscous oil. Purification of the product was obtained by dissolving in benzol and precipitating by means of alcohol. The thus purified product was a clear, rubbery material of low elasticity. Anaylsis of the product established Via/100 Via/210 V. I.

Sun 20W motor oil 275.8 45. 9 13 Sun 20W motor oil 3% copolymer 493 58. 1 69 The invention now having been described and illustrated, what is claimed is:

1. A lubricating composition comprising a mineral lubricating oil and between 0.5% and 5% by weight an oil-soluble co-polymer of a diolefin and an unsaturated ester.

2. A lubricating composition according to claim 1 in which theoil-soluble co-polymer is formed from a conjugated diolefln in which both double bonds are terminal.

3. A lubricating composition according to claim 1 in which the unsaturated ester is formed from an alcohol of at least eight carbon atoms.

4. A lubricating composition according to claim 1 in which the unsaturated ester is formed from an unsaturated acid and a saturated alcohol of at least eight carbon atoms.

5. A lubricating composition comprising a mineral lubricating oil and between 0.5% and 5% by weight of a co-polymer of a diolefin of conjugated structure having terminal unsaturated groupings and an ester of an acrylic acid.

6. A lubricating composition according to claim 5 in which the diolefln of conjugated structure having terminal unsaturated groupings is 2-3 dimethyl butadiene.

7. A lubricating composition according to claim 5 in which the diolefln of conJugated structure having terminal unsaturated groupings is isoprene.

8. A lubricating composition according to claim 5'in which the diolefln oi. conjugated structure having terminal unsaturated groupings is butadiene.

" ANTHONY H. GLEASON. 

